Crankshaft damper



CONNOR July 4, 1950 CRANKSHAFT- DAMPER 4 Sheets-Sheet 1 Filed Sept. 24, 1945 mm U Q QN J in f 4/2? July 4, 1950 .B. E. OCONNOR CRANKSHAFT DAMPER 4 Sheets-Sheet 2 Filed Sept. 24, 1945 July 4, 1950 B. E. O'CONNOR 2,514,136

CRANKSHAFT DAMPER Filed Sept. 24, 1945 4 Sheets-Sheet s I [fiver-Jar" Bag/M20 [Y O'C'wwvoe Wag/W fizz Patented July 4,1950

CRANKSHAFT DAMPER Bernard E. O'Connor, Buffalo, N. Y., assignor to Houdaille-Hershey Corporation, Detroit, Mich., a corporation of Michigan Application September 24, 1945, Serial No. 618,099

This invention relates to improvements in vibration dampers and is more especially directed to overcoming the problem of torsional oscillations or vibrations in rotary masses such as the crankshafts of rotating machinery, of which internal combustion engines are a prime example, whereby to reduce or eliminate wear and noise and avoid fatigue failure which are resultants of such vibrations.

As is well known, of course, torsional oscillations or vibrations arise in rotary crankshafts from the application of driving energy thereto periodically as, for example, in piston operated machines such as certain steam engines and in internal combustion engines where gases expanding with explosive force are relied upon to drive pistons connected to the crankshafts. As the energy is released to such a crankshaft, there is a more or less severe torsional or twisting impact at the point of application of the energy tending to cause the immediately affected portion of the crankshaft to overrun the remainder of the shaft. This reacts in a torsional vibration throughout the shaft. At high frequency, such torsional vibration may, and often does, attain a disagreeable, damaging and very often dangerous amplitude. The greatest danger, as will be appreciated, resides in the ultimate fatigue failure of the vibrated member due to the torsional vibrations, although the damaging effects of the vibrations on associated mechanism may in most instances be the main reason for desiring to eliminate them.

Heretofore, it has been proposed to dampen torsional vibration by means of frictional devices. However, such frictional devices have certain inherent shortcomings among which may be mentioned rapidly declining efficiency due to wear, undue sensitivity to atmospheric changes, undesirable reaction to temperature changes, and the like.

An important object of the present invention is to avoid the use of frictional means for damping torsional oscillations or vibrations but instead to utilize the shear resistance of viscous fluids in overcoming the problem.

Another object is to obtain higher efllciency in crankshaft dampers.

Still another object of the invention is to provide a crankshaft damper which is free from efliciency losses due to wearing of parts and therefore at all times maintains peak emciency.

A further object of the invention is to provide improved crankshaft dampers which remain sub stantially unaffected by atmospheric changes.

Yet another object of the invention is to pro- 13 Claims. (Cl. 74-574) vide crankshaft damping means which remain highly efiicient throughout a wide temperature range that may be encountered in use, and more especially retain a high degree of operating efficiency at low temperatures although the optimum adjustment is established for a relatively higher normal operating temperature.

A still further object of the invention is to provide crankshaft damping means which are highly adaptable to meet various operational requirements.

-An additional object is to provide an improved method of damping torsional oscillations or vibrations in crankshafts.

Other objects, features and advantages of the present invention will be readily apparent from the following description taken in connection with the accompanying drawings, in which:

Figure 1 is a diametrical sectional view through a crankshaft damper embodying features of the present invention;

Figure 2 is a vertical sectional view through the damper taken substantially along the line 11-11 of Figure 1;

Figure 3 is a diametrical sectional view through a modified form of the damper;

Figure 4 is a vertical sectional view taken on the line IV-IV of Figure 3;

Figure 5 is a diametrical sectional view of a further modified form of the crankshaft damper;

Figure 6 is a front elevational view, on a reduced scale, of the damper shown in Figure 5;

Figure '7 is a fragmentary diametrical sectional view on an enlarged scale through a slight modification of the damper shown in Figure 5;

Figure 8 is a diametrical sectional view through still another form of the crankshaft damper; and

Figure 9 is a vertical sectional view taken substantially in the plane of line IX-IX of Figure 8.

Although several forms of torsional oscillation or vibration dampers according to the present invention for rotating machinery and particularly for shafts such as crankshafts have been shown and will hereinafter be described in detail, all forms have certain characteristics in common.

An important feature of the dampers resides in the use of a viscous fluid such as a silicone to resist relative motion between a damping inertia mass and a structure securedfor rotation with a torsionally oscillating or vibrating mass such as a driven rotary shaft or crankshaft of a machine. More specifically, a flywheel is so disposed in spaced, relatively movable relation to a housing or to internal surfaces carried by the housing,

. that when the housing or such surfaces rotate 3 with the torsionally oscillating mass such as a crankshaft a thin film of the viscous fluid intervening between the opposing working surfaces of or associated with the flywheel and the adjacent surfaces rotating with the shaft causes the flywheel to rotate with the shaft due to the inherent shear resistance of the viscous liquid. That is, the viscous fluid is present between the opposing parallel working surfaces of the flywheel and housing in fllms which are thicker than a mere lubricating film but which are of less thickness than a layer which will produce only a fluid drag relationship. Stated another way, the shear film of viscous fluid is the result of an essentially linear velocity gradient spacing between the opposing parallel working surfaces of the members with relation to the viscosity of the damping fluid rather than a non-linear velocity gradient relationship. As the shaft tends to oscillate or vibrate in operation the same characteristics-of the viscous fluid which cause rotation of the flywheel with the shaft also resist the torsional oscillatory or vibrational movements of the shaft superimposed upon the normal rotation of the shaft. The force necessary to shear the viscous flim between the flywheel surfaces and the adjacent work surfaces of the housing is proportional to the relative angular velocity between the flywheel and the housing work surfaces. The optimum proportion of the resistance of the viscous film to the moment of inertia of the flywheel is easily calculated for any specific installation.

In certain embodiments of the invention, instead of having the damping mass or flywheel relatively independently movably mounted in association with the mass subject to torsional oscillation and rotatable therewith entirely as a result of the shear resistance of the viscous fluid, the flywheel is torsionally connected to the main rotating and torsionally osciilatable mass. The inertia, of the flywheel tending to resist torsional vibrations of the main mass is then harnessed to dampen the torsional vibrations through the medium of a film of the viscous fluid acting between the flywheel surfaces and closely adjacent working surfaces within the flywheel housing, and also through the resistance of a damper spring.

Having reference now to the form of the invention shown in Figures 1 and 2 and which has been especially devised for use with the crankshaft of an internal combustion engine such as an automobile, a flywheel i 5 is relatively rotatably and axially movably mounted within a chamber it provided by a housing formed in part by a fan belt pulley H which includes a hub l8 adapted to be mounted upon the outer end portion of a crankshaft IS. The hub 18 is formed to extend substantially to opposite sides of the flywheel l5 and is provided with means such as a key slot 20 to receive a key 2| to maintain the hub for joint rotation with the shaft it. A substantially cupshaped shell 22 provides a closure for the chamber l6 and completes the flywheel housing. The shell 22 has its margin in smug embracing engagement with an outer marginal flange 22 extending axially from the adjacent front side of the pulley l1. Means for securing the shell in place on the flange 23 may comprise a circumferentially spaced series of pins or stakes 24. A fluid-seal is provided by packing 25 carried within a groove 21 in the shell-opposing face of the flange 23.

A bearing for rotation of the flywheel I! about the forwardly projecting end portion of the hub i2 .is provided by a bushing 28 which is secured in assembly by the adjacent wall of the housing shell 22 driven axially thereagainst by means of a nut 2| threadedabout the protruding forward end of the hub IO and is prevented from loosening by means such as a set screw I0. A liquid-tight seal is provided by packing 3! disposed within an annular groove 22 in the hub at the juncture of the cover 22 and the bushing 28.

The interior of the chamber I is so proportioned with respect to the dimensions of the flywheel ii that only a very narrow spacing persists between the surfaces of the flywheel at its periphery and axial sides and the opposing work surfaces of the housing. Such spaces are filled with a viscous fluid such as a selected silicone, a commercial example of which may be identified as Dow-Corning fluid No. 200, having a viscosity rating of approximately 30,000 centistokes at 77 F. For the best results it is recommended that the chamber I6 be fllled at a temperature of approximately 200 to 250 F. A good working clearance for such a fluid is approximately /64 of an inch between the surfaces of the flywheel i5 and the working surfaces of the housing within the chamber It. To obtain uniformity of distribution of the viscous fluid for providing a uniform viscous film over the flywheel, a balanced plurality of axially extending liquid distribution holes 33 may be provided to extend through the flywheel l5 adjacent to its inner or hub periphery and communicating with similar fluid distribution annular rabbet grooves 38 in the opposite hub margins of the flywheel. Communicating with the fluid distribution system provided by the holes 33 and the grooves 36 is a filling open ing 35, preferably formed in the web of the pulley wheel I! and closed by a screw plug 31.

In operation, the hub l8 and thus the flywheel housing rotates with the shaft l9 and is thereby also subject to any torsional vibrations or oscillation of the shaft. The only driving connection between the flywheel l5 and the hub I8 is through the medium of the film of viscous fluid acting between the surfaces of the fly wheel i5 and the working surfaces within the chamber i6. This fluid driving connection more or less gradually induces the flywheel to rotate at the speed of the shaft i9, centrifugal force driving the viscous fluid uniformly throughout the working clearances between the flywheel and the housing. The inertia of the flywheel causes it to resist sudden variations in rotary momentum such as are the result of torsional oscillations or vibrations. This resistance is transmitted through the viscous fluid film and the walls-of the housing within the chamber It to the hub 18 and thereby to the shaft l9. As a result, the torsional vibrations or oscillations are dampened and prevented from having any deleterious effect upon either the shaft or associated mechanism. Due to the freedom of axial movement of the flywheel IS, the centrifugal pressure of the viscous damping fluid working in the axial spacm between the flywheel and the housing causes the flywheel during operation to assume an equalized or self-centered position within the chamber is so that the axial spaces are as nearly perfectly uniform as practicable.

Where the magnitude of the torsional vibrations or oscillations is such as to require greater damping resistance than afforded by the working surface area provided by the damper disclosed in Figures 1 and 2, a modified version such as shown in Figures 3 and 4 may be employed wherein the working area upon which the viscous damping fluid is operative is greatly extended by the provision of means such as interleaved disks.

In this form of the damper, a flywheel 38 has in preferably fixed, such as press fitted assembly therewith a bearing bushing 39 which is axially slidable and freely rotatable about a hub 48. The latter is adapted to be carried by a shaft 4| subject to rotary oscillation or vibration superimposed upon it at normal operating speeds. A connection for joint rotation of the shaft and hub may be effected through the medium of a key 42 located in keying slots 43 and 44 in the hub and the shaft, respectively.

The flywheel 38 is formed with annular spacer shoulders 45 at its opposite axial sides adjacent the hub for maintaining surface-extending coaxial disks 4! in spaced relation thereto sufficient to accommodate in closely spaced relation therebetween disks 48 which are mounted fast within an enclosing housing 49 which provides a chamber 58 within which the flywheel 38 and the associated disks are disposed. The mass of the flywheel 38 may, of course, be as great or as small as desired and the disks 41 and 48 may be as thick or as thin and of such diameter as the particular circumstances warrant and their spacing with respect to each other and to the flywheel 38 may be appropriately adjusted with regard to the operating conditions to be encountered in use and the viscosity characteristics of the damping fluid within the chamber 58. Furthermore, the number of interleaved disks may be as great as would seem to be warranted for the damping action required.

As shown, an additional pair of outer flywheel disks H is provided to cooperate with an additional pair of housing disks 62. The outer flywheel disks 6i also cooperate in damping relation with the axial walls of the housing 48. Means for securing the flywheed disks 4! and Il for joint rotation with the flywheel 38 may, as shown, comprise rivets 53 extending through the disks and the hub portion of the flywheel at the spacer shoulders 45 in equidistantly annularly spaced relation, with appropriate spacers such as rings 54 interposed between the inner disks 4! and the outer disks and all being clamped solidly together by the rivets. Similarly, the housing disks 48 and 52 are clamped tightly into position and torsionally rigid with the housing 49 by anequidistantly annularly spaced series of rivets 55, spacers 51, 58 and 89 maintaining the preferred spacing between respectively the opposed faces of the spaced disks 48, the opposing faces of the disks 48 and 52, and the opposing surfaces of the disks 52 and the axial side walls of the housing 49 to which the disk mass is secured by the rivets 55.

In a simple construction, the housing 48 may comprise a two-part structure including a sub- 1 stantially cup-shaped member 68, providing an axial and the circumferential wall of the housing, and a closure disk 6| providing the opposite axial side wall of the housing. They are secured together where the annular wall of the housing member 68 contacts the closure disk 8| edgewise, as by welding 82, to provide a fluid 8' fllm between all of the opposed relatively movable surfaces of the damper. To accommodate the filling operation, and also to provide clearance for the heads of the flywheel rivets 83, the chamber members 88 and 8! are preferably formed with substantial off-set clearances and 81, respectively, adjacent to the hub 48. This provides a system of liquid distribution channels interiorly of the chamber. Each of 'the offsets 88 and 81 is preferablyprovided with an opening 88, one of which will serve as a filler opening during filling of the chamber 88, while the other opening 68 serves as an air vent during the same operation. After the chamber 49 has been filled with the viscous liquid, the openings 88 may be closed with fluid-sealing means such as respective solder seals 88. 7

As will now be apparent, the torsional vibration or oscillation damper of Figure 3 provides substantially multiplied area subject to the shear resistance of the viscous fluid therein so that the vibration or oscillation damping action of the flywheel 38 is rendered quite strong and positive in action. The mass of the flywheel 38 as well as the area thereof exposed to the viscous fluid film, and also the number, size. and effective 'areas of the co-operating disks can be conveniently calculated and constructed to meet any reasonable practical requirements. It may also be noted that in this form of the invention, similarly as in the form of the invention shown in Figures 1 and 2, the flywheel is self-aligning in operation due to the centrifugal force of the viscous fluid. It is therefore practical to allow the same free floating action of the-flywheel axially within the housing 48, with the attendant advantages in manufacturing tolerances in the various co-operating parts.

Some forms of rotating machinery, as for example, certain steam operated or Diesel operated machines having relatively heavy 'crankshafts, require large, heavy. duty dampers. Actual operating conditions may, however, present problems of inertia, momentum and torsional stresses and involve variable factors in operation which cannot be wholly anticipated in designing a vibration damping member such as the forms shown in Figures 1 to 3. In particular, since the motion of the main mass which is to be dampened can be transferred to the flywheel only by means of the viscous fluid medium, due to the relatively free floating mounting of the flywheel within its housing, individual adjustments may be required in connection with individual machines in order to secure greater or less resistance between the vibration-damping flywheel mass and the working surfaces rotating with the main mass. The motion of the flywheel mass with respect to the motion of the main mass is, of course, proportional to the power of resistance to motion of the viscous film between the flywheel and the working surfaces, and inversely proportional to the inertia of the flywheel. Therefore, a greater shear resistance.

in the viscous film between the relatively movable surfaces in the damper will result, up to certain limits, from reducing the spacing between the working surfaces, this having the effect of reducing the thickness and increasing the tenacity of the fllm. On the other hand, it may be necessary under certain conditions to increase the working space or clearance between the surfaces and thus release the flywheel for somewhat freer movement.

An adjustable damper which is particularly suitable for the purposes just mentioned is shown in Figures and 6 wherein a flywheel I! is jointly and independently rotatable within a housing H. A hub I! on the housing is adapted to be secured to the end of the shaft '13 which is of relatively large diameter and great mass. In this instance, both the flywheel I8 and the housing II are of relatively large diameter and substantially flat, disklike construction affording large cooperative working surfaces for the action of the viscous fllm therein.

In order to adapt the flywheel III for adjustment with respect to the spacing of the flywheel surfaces from at least the major side wall coopcrating working surfaces of the housing H, the flywheel is formed in two relatively adjustable sections, herein comprising similar flywheel disks i8 and I! which are normally cooperable in faceto-face relationship and can be axially adiusted to increase the over-all width of the flywheel. For efiecting such adiustment there are provided adjusting screws 'I'I, herein three in number disposed in equidistantly spaced balanced annular series, which are carried rotatably but not axially shiitable adjacent to the hub of the device by one of the disks, herein the disk 14. The screws T! have adjustable threaded engagement with the other disk T5 so that by turning the screws 11 the disks can be drawn tightly together or spread apart as required. The screws I1 are held against axial movement relative to the disk 14 by slotted heads 18 thereon and cooperating snap rings 19 fitting in axial grooves 88 formed in the shanks of the screws in proper spaced relation to the heads 18 to receive the intervening thickness of the carrying disk 'Il. Turning of the screws 1? out of adjustment is prevented by means such as fiber locking rings 8! carried by the respective screws adjacent to their terminal ends. It will be clear, of course, that the screws 11 hold the disks 14 and 15 against relative rotation.

By preference, the housing H and the hub 12 are formed integrally as a casting providing an annular chamber 82 within which the flywheel 18 is closely accommodated and which in the casting is open at one side but is closed in the operative assembly by a cover 83. The latter may be formed to internest snugly with an axially projecting marginal portion of the peripheral wall of the housing El and is secured in a tight, rigid joint therewith as by welding 84. The cover is similarly associated and secured to the cooperating portion of the hub 12 and sealed as by welding 85. Adjustment access to the screws I1 is provided for through appropriately dimensioned and located openings 81 in the closure wall 83 and which openings are closed by screw plugs 88 effecting a fluid-tight seal through the medium of respective sealing washers 89.

Viscous damping liquid may be introduced into the chamber 82 through any selected one of the access openings 81. The filling of liquid into the chamber 82 is facilitated by relatively equally opposite axial extensions of the chamber 82 adjacent to the hub 12 as provided by channel oil'sets 90 and Si in respectively the hub part of the side wall of the housing 'H'and the hub part of the cover wall 83. The fluid channels 58 and 9| also accommodate any protruding portions of the adjustment screws 11 within the fluid chamber.

Free relative rotation of the flywheel l8 and the housing H is facilitated by providing antifriction means such as bearing balls 92 between the inner diameters of the flywheel disks l4 and 18 and the hub 12. Accordingly. the disks I4 and I! may be provided with individual bearing races 8! and the bearing balls 82 may be of relatively small size running in respective grooves 9! in the flywheel races 92 but running on a common cylindrical race on the hub 12. Th s permits free axial adjustment of the flywheel halves 14' and 15 and bodily axial movement of the flywheel 18 for alignment and self-centering 0f the flywheel within the chamber 82 under the centrifugal action of the viscous fluid during operation. It may also be noted that the space between the bearing races 83 and 95 affords fluid communication between the channels and 51.

Where preferred, ring bearings 91 may be substituted, as shown in Figure 7, for the ball bearlugs 92.

Removable attachment of the hub 72 to the end of the shaft 13 may be efiected through the medium of bolts 98. For quick attachment purposes the bolts 98 should be as few in number as practicable, and yet there must be a high degree of torsional strain resistance in the connection with the shaft for obvious reasons. Accordingly, there may be three of the bolts 98 equidistantly annularly spaced as shown in Figure 6, altermating with close fitting pins 9s. A quick-detachable relationship of the damper and the shaft 13 is particularly desirable in order to permit removal of the member for adjustment purposes after it has been tried out on the shaft 13 and the desirability of adjustment "determined. For this purpose it is a relatively simple matter to remove the three attaching screws 98, and slip the pins 98 out of their sockets. The damper is then laid on its side with the access openings 81 up, and the closure plugs 88 are removed to expose the adjusting screws 18. Should the adiusting screws 18 be out of register with the access openings 81, the flywheel Hi can easily be turned until registration is efiected, by means of a suitable tool such as a screw driver or the like inserted through any of the access openings and received in a leverage pit I88. A uniform annular series of the leverage pits Hi0 may be provided in the flywheel disk l4 between each pair of adjusting screws 78. After appropriate adjustments have been made to increase or decrease the efiective spacing between the inner side walls of the flywheel disks 14 and 15 and the opposing working surfaces of the housing H and the closure wall 83, reassembly of the damper into working order with the shaft 13 can be rapidly efl'ected by re-registr-ation of the pins and replacing the attaching screws 98.

Up to this point the various forms of torsional vibration or oscillation dampers described have been of the more or less free running type in that the flywheel in each instance has been free to rotate relative to its housing and therefore relative to the associated shaft except for the viscous connection afiorded by the viscous liquid working between the closely spaced surfaces provided for this purpose.

However, the invention also contemplates the provision of what may be termed as a tuned damper in which a flexible or torsional mechanical connection is effected between the flywheel structure and the vibrating mass through the medium of the hub by which the damper is connected to the vibrating mass. As a result of such connection, the vibrations or torsional oscillations l 01 the main mass, such as the driven rotary shaft of a machine, are imparted, more or less, to the flywheel which is thus also vibrated or oscillated. But due to the great diflerence in the respective memes, the flywheel will tend to vibrate or oscillate at a different amplitude which is out of phase with the amplitude of vibration or oscillation of the main vibrating mass. Therefore, there is a tendency towards relative motion of the flywheel and the main mass which, when resisted by the viscous film intervening between the active surface of the flywheel and opposing working surfaces within the flywheel housing, has the effect of counteracting and dampening the vibration or oscillation in the main mass. A tuned damper is actually much more efilcient than a free running damper when used for the same purpose, but must be especially designed for each application to which it is to be put. This does not mean, of course, that each damper must be individually designed, but that for each type of rotary mass to be damped and having a known frequency of amplitude of torsional vibration or oscillation, a damper must be endowed with special frequency responses which will cause it to function as desired for that particular practical application. That is, the proportions of the flywheel and its resilient connection must be such that the flywheel has a natural frequency somewhat lower than the natural frequency of the main mass. In this manner, when the frequency of the exciting force in the main mass approaches the natural frequency of the main mass and the damper combination, the damper flywheel vibrates with an amplitude which is large in proportion to the amplitude of vibration of the main mass and energy is then absorbed due to the relative motion between the flywheel and the housing which is overcome by the resisting force of the viscous film.

In one form of the tuned torsional damper, as shown in Figures 8 and 9, a ring-type of flywheel IOI of substantially greater internal diameter than a hub I02 is connected to the hub concentrically through the medium of a coiled torsion spring I03. The spring I03 is in the nature of an untensioned or open clock spring having its outer end formed with a connecting loop I by which it is connected through the medium of a pin I05 to the flywheel I M within an annular radial groove I06. The inner end of the spring I03 is formed with a loop I 01 by which it is connected as by means of a pin I08 within a peripheral recess I09 provided therefor in the hub I02. With this arrangement, it will be obvious that relative rotational movement of the flywheel IN and hub I02 is permitted within certain limits by flexure of the coil spring I03 but that the tendency of the spring I 03 is at all times to return to the normal or neutral relative position of the flywheel and hub. As a result, while steady rotation in one direction of the hub I02 will cause the flywheel IN to rotate therewith due to the connection afforded by the spring I03, any variations in speed such as accompany torsional vibration or oscillation are resisted by the flywheel. Such resistance is transmitted to a certain extent to the hub I02 through the torsion spring I03. If the flywheel IOI were allowed to operate freely and in the clear, a continuous frequency of vibration or oscillation in the hub I02 would tend through the spring I03 to generate a sympathetic vibration or oscillation in the flywheel IOI. However, the flywheel IOI is enclosed within a housing IIO which is rigid with the hub I02 and closely approaches all adjacent surfaces Of the and the housingare filled with a viscous damping fluid to provide a continuous viscous fllm on and between the closely approaching surfaces.

Therefore all tendency during operation toward relative oscillaton of the flywheel IM and the hub I02 is strongly resisted by the viscous film. As a result, torsional oscillation or vibration in the hub I02 is effectively dampened.

An economical construction for the housing IIO comprises a two-part structure including a substantially cup-shaped shell III which provides one side and the peripheral wail of the housing and is secured to the hub I02 within a rabbet groove H2 in the latter. A fluid-tight and torsionally solid junction between the shell III and the hub is eflected as by means of welding Ill. The opposite wall of the housing I I0 comprises a closure wall plate III interfltting with the hub I02 in a rabbet groove II! at the opposite end of the hub and rigidly secured in fluid-tight relation to the hub as by means of welding III. A rigid, fluid-tight connection of the closure wall II! with the peripheral wall of the cup-shaped member I I I may be effected as by means of weldin at Ill.

The hub I02 is adapted to be fixedly attached to a shaft I I0 in which the vibrations or torsional oscillations are to be dampened, as by means of a keyed connection including a key I20 received within a slot I2I in the shaft and an axial groove I22 within the inner periphery of the hub.

Space for an ample supply of viscous fluid within the housing H0 is afforded by the chamber area between the flywheel IM and the hub I02 within which the torsion spring I 03 occupies only a fraction of the total and because of its open nature permits free distribution of fluid throughout the chamber. Communicating with such chamber area is a pair of small openings I23 and I24 preferably respectively in the housing shell III and in the cover wall I, and both adjacent to the hub I02. One of these openingsmay actually receive the fluid therethrough and the other serve as a vent opening. After the damper has been filled both of the openings I23 and I 24 are sealed by such means as a solder seal I25.

From the foregoing it will be apparent that the present invention provides an admirably simple, compact and eflicient type of vibration or oscillation damper for a torsional member subject to rotary vibrations or oscillations during operation and which. because of the relatively movable relationship of the stabilizing means or flywheel is practically free from all frictional contact with associated parts and is actually maintained in spaced relation with such parts, as for example the walls of the enclosing housing. Further, a constantly lubricated relationship is afforded by the viscous fluid which forms the relative motion resisting film between the working surfaces of the parts. Thus, the structure is entirely free from any possibility of wear. This assures complete efliciency in performance at all' times. Furthermore, by proper selection of the viscous damping fluid very little, and for the most part inconsequential, variation in efliciency will be encountered due to temperature variations. For example, it has been found that by the use of a silicone fluid a damper of the present invention adapted forefilciency at F. will be more than 75% efilcient at 0 F.

In addition, provision is made for effecting desirable adjustments to accommodate special working conditions. Even though the rotating ingtbesame.

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9. In combination in a vibration damper, a housing structure providing a fluid-tight chamber, an inertia mass structure housed within said chamber and relatively movable therein, and a viscous damping fluid within the'housing, said housing structure and said inertia mass structure having opposed parallel working surfaces which are in essentially linear velocity gradient spacing relative to the viscosity of the damping fluid and have a shear film of the fluid therebetween, such shear film being thicker than a mere lubricating film but being of less thickness than a layer of the fluid which would afford only a non-linear velocity gradient relationship, said shear fllm of the fluid acting between said working surfaces to resist relative parallel movement thereof 10. In combination in a vibration damper, a housing structure providing a fluid-tight chamber, an inertia mass structure housed within said chamber and relatively movable therein, and a viscous damping fluid comprising a silicone between said inertia mass structure and the housing structure, said housing structure and said inertia mass structure having opposed parallel working surfaces spaced apart sufficiently to avoid mechanical bearing of said surfaces but close enough together to limit the silicone fluid to a shear film operative to resist relative parallel vibratory movement between said working surfaces.

11. In combination in a vibration damper of the character described, a housing having a hub adapted to be attached to a mass to be damped such as a crankshaft and to rotate concentrically therewith, a flywheel concentrically rotatable and axially movably disposed within said housing, and a viscous damping fluid within said housing between the flywheel and the housing, said flywheel and said housing having axially facing surfaces in opposing relation and in operation being spaced out of bearing relation but being so close together as to limit the damping fluid to but a shear fllm therebetween, the damping fluid under centrifugal force in operation entering between said opposed surfaces and maintaining the shear film spacing therebetween to a uniform thickness at both sides of the flywheel and resisting relative torsional displacement of the flywheel and the housing by shear resistance.

12. In combination in a vibration damper, a housing structure providing a fluid-tight chamher and having a plurality of spaced parallel disks extending into said chamber, an inertia mass structure housed within said chamber and relatively movable therein, said inertia mass structure having a plurality of spaced parallel disks thereon interleaved with the disks of the housing structure, and a viscous damping fluid within the chamber, said housing structure and said inertia mass structure and the interleaved disks having opposed parallel working surfaces which are in essentially linear velocity gradient spacing relative to the viscosity of the damping fluid and having a shear film of the fluid therebetween, such shear film being thicker than a mere lubricating film but being of less thickness than a layer of the fluid which would afford only a nonlinear velocity gradient relationship, said shear film of the fluid acting between said working surfaces to resist relative parallel movement thereof.

13. In combination in a vibration damper, a housing structure providing a fluid-tight chamber, an inertia mass structure housed within said chamber and relatively movable therein, a viscous damping fluid within the housing, said housing structure and said inertia mass structure having opposed parallel working surfaces which are in essentially linear velocity gradient spacing relative to the viscosity of the damping fluid and have a shear fllm of the liquid therebetween, such shear film being thicker than a mere lubricating film but being of less thickness than a layer of the fluid which would afford only a nonlinear velocity gradient relationship, said shear film of the fluid acting between said working surfaces to resist relative parallel movement thereof, said housing structure including a hub, said inertia mass structure being of annular form and of substantially greater internal diameter than the diameter of the hub 50 as to leave a substantial space therebetween, and a spiral spring disposed around said hub and having its inner end connected to the hub and its outer end connected to the inertia mass structure to provide a resilient connection between the housing structure and the inertia, mass structure acting to resist relative movements of the housing and inertia mass structures in addition to the resistance to movement aforesaid of the viscous damping fluid.

BERNARD E. OCONNOR.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number Name Date 1,718,207 Anibal June 25, 1929 1,719,805 Hammond July 2, 1929 1,830,600 Fifleld Nov. 3, 1931 1,928,119 Vargha Sept, 26, 1933 1,962,367 Smythe June 12, 1934 2,002,699 Larsen May 28, 1935 2,013,109 Reynolds Sept. 3, 1935 6 ,369 Meyer Dec. 1, 1936 2,080,279 Kellogg May 11, 1937 94 Griffith Dec. 2, 1941 6 ,266 Clark Oct. 24, 1944 FOREIGN PATENTS Number Country Date 337,466 Great Britain May 20, 1939 349,906 Great Britain May 26, 1931 508,513 Great Britain July 3, 1939 

